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Group B Strep: 3rd Trimester Test

The Group B strep test is given to women in the 3rd trimester in preparation for delivery. 

Group B strep is a bacterial infection that babies can get during delivery and about 1 in 4 women have the Group B strep bacteria in their bodies. The test is given to determine if the mother needs antibiotics to prevent the transmission of the infection to her baby.

Group B strep bacteria naturally occurs, and expecting women with Group B strep do not have any symptoms. While in the uterus, the infection does not affect the baby. During a regular prenatal visit, your medical provider will use a cotton swab to take a culture of cells from the vagina. The test results usually take 48-72 hours. 

Some people are at higher risk for Group B strep, including women who:

  • Have had a previous positive test for Group B strep

  • Develop a fever during labor

  • Experience an extended time between water breaking and the baby being born (more than 18 hours)

  • Have previous medical conditions like cancer, heart disease, or diabetes

If you are Group B strep positive, your medical provider will give you an intravenous antibiotic during delivery. This prevents about 90% of infections in newborns. A small percentage of babies will experience late-onset Group B strep within 1-3 weeks of being born. 

Both babies who are born with or have late-onset Group B strep will receive antibiotics to treat the infection. Symptoms in newborns include: fever, difficulty feeding, irritability, breathing difficulties, and lack of energy. As the mother has already been tested for the bacteria, newborns can be quickly diagnosed and treated. Infants with Group B strep can develop meningitis, pneumonia, or sepsis. 

Screening for Group B strep bacteria has greatly reduced the risk of babies contracting it. Be sure to keep all your prenatal appointments in order to get important tests like this one.

The Tennessee Family Doulas team would love to help you learn more about the tests provided during pregnancy. Talk with us about our Doulas support services.



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